Production of high molecular weight polyethylene



M. R. CINES March v18, 195s PRODUCTION OF HIGH MOLECULAR WEIGHT POLYETHYLENE Filed July 2, 1954 3 Sheets-Sheet 1 250009 J2S.; E551,

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ATTO NEYS United States Patent PRODCTION F HIGH MOLECULAR WEIGHT POLYETHYLENE Martin R. Cines, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application July 2, 1954, Serial No. 441,129 Claims. (Cl. 260-88.1)

the presence of a catalyst as herein described by contact ing said gases with said solvent and'then conveying said ethylene contained in said solvent, in some cases together with some propylene, to a polymerization zone wherein the formation of solid polyolen is accomplished. In-

another aspect, the invention relates to the production ofsolid polyethylene by subjecting a non-reactive solvent containing ethylene and also containing absorbed propylene to propylene polymerizing conditions adapted to polymerize at least sufficient of said propylene so that in the ensuing ethylene polymerization, the propylene will enter only desirably into the solid product to be formed from said ethylene. In still another aspect of the invention, it relates to the production of polyethylene from a cracked hydrocarbon gas stream, containing acetylene, hydrogen and ethylene, which includes contacting said stream with a hydrogenation catalyst under conditions to hydrogenate acetylene to ethylene. In still another aspect of the invention, it relates to the feeding of a vaporous material, for example ethylene, into an absorber wherein the'vaporous material is absorbed into a solvent which will remain substantially unaffected in an ensuing conversion operation in which said vaporous material is converted, dividing the solution of said vaporous material in said solvent thus obtained into at least two portions, feeding a portion to a conversion zone for conversion of the vaporous material in the solvent, passing the solvent to-another conversion zone, passing the other portion of said solution to a stripper zone, therein causing the solution to yield up a substantial portion of said vaporous material and passing said vaporous material into the solvent passing to said another conversion zone.

There is at present considerable interest in solid polymers of ethylene, but in the manufacture of ethylene polymer from cracked gases, purification of the ethylene is a large part of the cost of the operation. My invention accomplishes the steps of absorption, purification, and polymerization in such a manner that the process can be operated with a minimum amount of compression and refrigeration and thus considerably cheaper and more eticiently than conventional processes. My invention primarily resides in the novel and advantageous manner in which the various steps have been combined to produce the desired result.

It has been found desirable to use a diluent, preferably isooctane, in the polymerization of ethylene to solid polymer over chromium oxide-silica-alumina catalyst.

In Serial No. 333,576, tiled January 27, 1953, now

ICC

abandoned, there is described and claimed a process for.v the polymerization of oleins, for example, ethylene, adrnixed with a hydrocarbon diluent inert and liquid under"v the conditions of the process in the presence of a com-4 posite catalyst comprising chromium oxide. Generally, the conditions and other operational details, given in Serial No. 333,576, where required, are applicable in the process of the present invention.

When the solvent of the present invention is a hydrocarbon, it preferably is a paraiiin and will include at least one parain having from 3 to 12 carbon atoms per molecule. Any hydrocarbon diluent which is relatively inert,- non-deleterious, and liquid under the reaction conditions of the process may be utilized. Diluents that have been used successfully include propane, isobutane, normal pentane, isopentane, and isooctane. The heavier diluents gave better results, probably because they are better solvents for the heavy polymer. However, very heavyj diluents have the disadvantage that they are more dicult'f to separate from the polymer.

My invention uses a solvent, as described, as the absorbing medium in an ethylene absorber and then, inoneembodiment of the invention, the absorber kettle productis fed to the catalyst without further treatment, or, Yas in another embodiment of the invention, a preliminaryplymerization of gases other than'ethylene is practiced;

In the drawings, the gures illustrate 'diagrar'nn'1ati-callythe two embodiments to which I havereferred. Although' the process is described with reference .to a cracking" furnace euent containing propylene and 'lighter materiabf it should be understood that the eluent maylcontain'f' minor amounts of heavier material.

i In Figure 1, a propane gas is pyrolytically treated to* produce an ethylene-containing gas which is hydrogenated," principally to convert acetylene to ethylene following" which the gases are subjected to propylene 'polymerizing` conditions. After removal of propylene polymers, to anextent desired, the gases are subjected, dissolved in a solvent, to ethylene polymerizing conditions in the pres-' ence of a catalyst, suitably and now preferably the.cata lyst which is described and referred to herein.

In Figure 2, cracked gases containing ethylene are contacted with a solvent, say isooctane, in an absorber following which propylene and then ethylene polymerizations are effected. Upon polymer removal and fractionation, the solvent is returned for further use in the absorber.

In Figure 3 is shown an embodiment of the invention'. in which a saturated hydrocarbon gas is cracked to pro-v duce a stream from which acetylene is removed followed by removal of propylene. The acetyleneis removed by catalytic hydrogenation and the propylene is removed by catalytic polymerization. Catalytically polymerized gases are treated in an absorber by absorption contact with a light oil obtaining ethylene which is then absorbed in a hydrocarbon liquid and subjected to polymerization under conditions of polymerization to form polyethylene, following which the polymer is obtained by hashing therefromA unreacted gases and materials lighter than said polymer. Some propylene can be present in the ethylene in which, event some interpolymer of ethylene and propylene will be present in the final product. The material ashed from the product is fractionated to remove all materials heavier than the said hydrocarbon liquid which hydrocarbon liquid in this instance is isooctane, which passes over- 4 In Figure 4 is shown an embodiment in which acetylenefree, ethylene-containing gaseous feed, is absorbed in the Vdiluent which can be isooctane,. following which any4 propylene which has been absorbed is polymerized in the diluent by subjecting the entire stream to polymerization conditions whereupon together with recycle ethylene, the said stream is subjected to polyethylene-formingconditionsV in the presence of the catalyst without prior removal of propylene polymer. The remainder pf the operation is. then conducted substantially as generally described for Figure 3 hereof.

InFigure 5 is shown an embodiment of the feature of thisrv invention according to which the solvent containing the absorbed gases is divided into at least two streams, one stream is sentl to a tirst reactor and the other to a stripper to obtain from said stripper gases for reintroduction into said solvent at a point downsteam ofthe rst reactor.

Each of thel embodiments of the invention has distinct advantages but a feature common to all is the use of the ethylene absorbing medium as a diluent in the ethylene polymerization.

TheY polymer number designations` used in this disclosure are numbers designating the major and minor constituents ofthe polymer. The individual numbers refer. to the number of carbon atoms in the monomer, for instance, 2 is for ethylene and 3 is for propylene. The first number in order is the major constituent and the other is theminor, for instance, polymer 23. contains more ethylene than propylene and polymer 20 is considered to be all ethylene.

In Figure 1, propane is fed to a thermal cracking furnace 2, preferably a Selas furnace. The etliuent from thiscracking step is a mixture of acetylene, ethylene, propylene, hydrogen, methane, propane, andv heavier material. Thel gaseous portion of, this kstream will henceforthbe referred tcras-a-crackedfgas, stream. This stream in the gas-phase isthen passed,` in; zone. 3, over a catalyst, for example, a palladium catalyst, for-the; selective hydrogenationof acetylene to ethylene. This stream, still in the gas, phase, is passed, in zone 4,'0ver a propylene polymerization catalyst, such as a phosphoric acid catalyst, where the propylene is polymerized, and the ethylene is unatected. The effluent from this polymerization step is fed to a scrubber 5 wherein a light oil introduced at 6 is used to absorb the propylene polymer which is removed at 7. The stream is then fed to the ethylene absorber 8 where the ethylene and heavier components are absorbed inthe diluent isoocatane introduced at 9. The absorberV kettle. product which is a solution of isooctane, ethylene, ethane, propylene and propane is fed to a chromium oxide-alumina-silica catalyst in zone 10 at conditions selective for the polymerization of ethylene to solid polymer 23. This polymer, the isooctane, and Unreacted gaseous hydrocarbon are separated from each other by conventional means in zone 11 and the isoctane is recycled to absorber 8. Hydrogen and methane are vented from the process at 12. When desired, the isooctane stream can be treated to remove other gases accumulated therein, for example, ethane.

Referring now to Figure 2, an essentially acetylenefree, cracked gas stream is fed to absorber 2t) wherein ethylene and heavier gases are absorbed by a solvent or diluent, in this case, isoctane introduced through 21. Ordinarily, the stream will contain at most only a small amount of acetylene and any acetylene present will be polymerized along with the other olens present. The absorber kettle product is fed in the liquid phase to a catalyst case 22 containing a phosphoric acid catalyst and conditions are maintained such that essentially all of the propylene, butylenes, etc., are polymerized and ethylene is unaffected. The eiuent from this catalyst case is fed without any intermediate purification to theI ethylene polymerization catalyst 230. 'Ihe products of the rst polymerization step are not affected in the second polymerization step and act as diluents. The eluent from the. ethylene polymerization catalyst is fed to dash chamber 24 wherein essentially pure polyethylene, which is.

solid at room temperature (polymer 20) is removed. The components of the vapor from the tlash chamber, taken overhead through conduit 25, are then separated by any desired means. One method for this separation is shown on the drawing; the overhead from flash chamber 24 is introduced into fractionator 26 through line 25; isoctane and lighter material is taken overhead from fractionator 26 and is fed to fractionator 27. The kettle product from fractionator 27 is the isoctane diluent which is recycled to the absorber. Polymer-containing compounds having twelve and more carbon atoms to the molecule are removed from the bottom of fractionator 26. Unreacted gases and propylene dimer are taken overhead from fractionator 27.

From the foregoing descriptions, it will be evident to one skilled in the art that this invention minimizes the use of expensive compression and refrigeration equipment which is usually a large part of an ethylene purication plant.

Referring now to Figure 3, there is shown the pyrolysis in a furnace 39 of a hydrocarbon gas such as ethane, propane, butane, or a mixture of two or more of these gases, butane being a preferred feed in the invention, followed by a compression by compressor 31 of the cracked eluent prior to an acetylene removal step 32, if desired, following which the gases are catalytically polymerized to polymerize propylene therein in catalytic polymerization zone 33, following which propylene and other undesired materials such as propane and heavier materials are absorbed from the stream in polymer absorber zone 34. As understood in the art, the pyrolysis of hydrocarbons results in some heavier materials which desirably are removed prior to the acetylene removal step by means not shown. The acetylene can be removed by hydrogenation over platinum, palladium, nickel sulfide, or other suitable catalyst. A process for the removal of acetylene from gases containing the same is described and claimed in copending application, Serial No. 363,400, tiled June 22, 1953, by Gene Nowlin, now U. S.- Patent No. 2,775,634. In said application, the removal of acetylene is accomplished employing a catalyst.

In the embodiment shown, employing nickel sulde catalyst, the pressure during the acetylene removal will be in the neighborhood about fifty pounds per square inch absolute and the temperature will be in the range 125- 350" C. (257-662 F.). Thus the furnace eiuent is compressed to about 35-75 pounds per square inch gauge.

As noted elsewhere herein, a phosphoric acid-type polymerization catalyst is suited to the polymerization of propylene. Such catalyst can be employed at a temperature in the range of about 25G600 F. and, in any event, a desirable or optimum temperature for this step can be determined in the case of each catalyst according to procedures well understood by those skilled in the art, given 'that they have been provided with this disclosure.

In polymer absorber zone 34, the absorber mediun can be a light oil which can he a miner seal oil, which is suitable in most instances, and the polymerization eiuent will be fed to the absorber which operates in the range of 50-400 pounds per square inch gauge and about 125 F. and the absorber operated to obtain overhead the gases which are desirable in the ethylene absorber zone 35; polymer together with propane, and heavier materials being removed as bottoms from absorber zone 34, from which bottoms the absorber uid can be obtained by a stripping operation as well understood in the art and which is not shown on the drawing for sake of simplicity. In the ethylene absorber, a pressure and temperature are maintained to recover about percent of the ethylene from the hydrocarbon stream and, as understood by one skilled in the art, the temperature and pressure will vary depending upon the composition of the gases and other factorsv involved in absorption. The temperature in the ethylene absorber will be in the range of GO-+90 F. and the pressure will be in the range of 50-400 pounds per square inch gauge.

In ethylene absorber 35, the absorbing medium will be, as stated, a liquid suitable to act as diluent in the ensuing polymerization of ethylene to polyethylene and this absorber medium in this embodiment is isooctane. The ethylene in solution in the isooctane is passed to catalytic zone 36 in which a catalyst, for example, that described in above-mentioned Serial No. 333,576, can be employed. The temperature in zone 36 will be about 300 F. and the pressure will be about 400 pounds per square inch gauge with preferably about a 20-30 rise in temperature over the catalyst. The temperature can vary and a range of 22S-350 F. is now preferred. ln this embodiment about 2 weight percent ethylene is dissolved in the isooctane and the pressure obtained is suicient to ensure liquid phase operation. With isooctane, the pressure can be in the range S50-400 pounds per square inch gauge. Within this range of pressure it is possible to vary the concentration of ethylene of from about l to 5 weight percent of the total isooctane-ethylene mixture and to suiciently maintain the liquid phase for desirable operation.

Leaving polymerization zone 36 at a temperature of about'320 F. to 330 F., in the embodiment described, the eluent is passed through heater 37 and a pressure reduction valve 38 into a ash chamber 39 wherein flashing under reduced pressure is conducted. Normally solid but presently liquid polymer is removed from the bottom of liash chamber 39 at a temperature of about 260 F. which is obtained when ash chamber 39 is operated at about 20 pounds per square inch gauge. As noted, the polymer can contain some propylene and in the embodiment described contains propylene as polymer combined in the polyethylene. n Vapor from the flash chamber, though it can be passed through a series of flashers operative in any suitable sequence which may be desired in modilcation of the embodiment, is passed to polymer separation zone 40 in which all material heavier than isooctane is removed as bottoms. Lighter material taken overhead from fractionator 40 is passed to a gas separator 41 from which non-condensed gas can be fed to recycle compressor 42 and from which gas separator liquid phase is passed to recycle column 43 from the bottom of which isooctane is recycled to ethylene absorber 35 to absorb additional quantities of ethylene in the operation. Recycle column 43 is operated to remove from the isooctane diluent substantially all propylene dimer which is formed in polymerization zone 35 and in the embodiment described gases containing ethylene are recovered from the propylene dimer in gas separator 44 and recycled to compressor 42. In the embodiment, column 40 can be operated at a pressure of from substantially atmospheric to about 15 pounds per square inch gauge and at a temperature to remove as bottoms the said material heavier than isooctane. Column 43 is operated substantially at atmospheric pressure.

As understood in the art from time to time a purging operation can be conducted upon the gas streams leaving gas separators 41 and 44.

Referring now to Figure 4, the operation described for Figure 2. is modified to show the recovery of gases as described in Figure 4. Thus, acetylene-free feed is contacted with isooctane in ethylene absorber 50 whereupon ethylene' is absorbed together with propylene which may be present, hydrogen and methane being removed as overhead. The isooctane diluent containing ethylene and said propylene is subjected' to propylene polymerizing conditions in polymerization zone 51 from which together withrecycled gases fed thereinto by means of compressor 5 2 the eduent from zone 51 is passed directly to polyethylene-forming zone 53. The operation of heater 54, ash zone 55, and fractionating zones 57 and 58 and their respective gas separators 58 and 59 are substantially as 75 heretofore described in connection with Figure 3. A heat.

exchanger 56 is employed in this embodiment to supply or remove heat from the material entering fractionator 57 in the event that the said material ldoes not contain the proper amount of heat to accomplish the separation desired to be effected in fractionator 57. Thus, heat exchanger 56 is adapted to heat or to cool the stream entering the fractionator and, preferably, is a cooler.

Referring now to Figure 5, a gas stream containing ethylene is passed by way of conduit 60 into absorber 61. ln absorber 61 the gas stream is contacted with a suitable solvent, in this instance isooctane, which removes from the gas stream substantially all of its contained ethylene together with a minor proportion of other gases. The solvent is introduced through conduit 62. gas leaves absorber 61 by way of conduit 6'3 and solvent containing absorbed ethylene and other gases-is withdrawn from absorber 61 by way of conduit 64 pumped to a higher pressure than that prevailing in polymerization reactors, to be described, by means of pump 65 and passed by way of conduit 66 into conduits 67 and 68. The portion of solvent containing ethylene and other gases which is passing through conduit 67 enters polymerization reactor 69 and is therein subjected to polymerization conditions. This reactor can be a reactor in which substantially all or only a portion of the ethylene is polymerized. Generally, the conditions for this reactor will be selected so that a substantial proportion of the gases contained in the isooctane are polymerized. Conditions already described herein are suitable for zone 69. From zone 69 the solvent, containing polymer, is passed by way of conduit 70 into polymerization reactor 71. Polymerization reactor 71 can be operated under conditions prevailing in reactor 69 and is preferably so operated. The stream passing through conduit 68 is passed into stripper 72 provided Withheating coils 73 and therein heated to cause liberation of a substantial proportion of its contained ethylene which is taken overhead through conduit 74 and conduit 75 and passed into conduit 70 wherein it dissolves inthe solvent and polymer phase passing from reactor 69 to reactor 71. From reactor 71 there is obtained a solvent and polymer mixture which is treated to recover solvent for reuse in the system and polymer as product. In order to maintain the desired concentration of ethylene in line 67, it may be desirable to add either solvent from line 76 or ethylene from line 75. To this end, cross-over conduits 77 and 78 are provided, equipped with suitable valves and/orv pumps, if necessary, not'shown.

lt will be noted that in Figure 5 only one pump is employed. The operation of Figure 5 is highly advantageous because it yields a stream of high pressure ethylene for introduction at a plurality of points downstream of the first reactor, or into a plurality of points along the line of llow through the first reactor, to replenish the ethylene as it is converted, without recourse to additional compressors. Of course, when absorber 61 is operated at a pressure which is in excess of that of the polymerization reactors by an amount sulcient to cause proper ilcw, pump 65 is not necessary. In some instances, it may be desirable to use a pump in line 68 if the pressure drop in stripper 72 is not less than the pressure drop in reactor 69. In any event, one skilled in this art can modify the valving and piping, somewhat, without departing from vthe essential concept of the claimed invention.

The embodiment of the feature of the invention just described provides a stream of high pressure ethylene by a method which requires a reduced amount of vapor phase compression. It has been found that the etliciency of an ethylene polymerization process can be improved by the addition of ethylene to one or more points in the ethylene reactor. This embodiment renders the overall process of the present invention more llexible because, as described, the operation ofthe stripper provides means Residue for directly controlling the ethylene content of the reactor feed.

The optimum conditions to be employed in the various steps of the described embodiments can be readily determined and are within the skill of one skilled in the art in possession of this disclosure. Catalysis which can be employed in the polymerization of propylene are well known in the art.

The following is a tabulation of a representative materials balance of a speciiic operation according to one embodiment of the invention in which an ethane feed part of the solvent and unreacted ethylene and as bottoms polymer dissolved in some solvent. The bottoms are treated to remove therefrom the remaining solvent thus obtaining the desired polymer. In the polymerization of ethylene in the presence of some propylene, some propylene dimer is formed and can be recovered from the ashed overhead, as herein described. The operation here exemplilied is substantially that of Figure 3 hereof. The operational steps and the equipment required are, therefore, to be understood to be embodied in this exeinplijication.

Propy- Propy- Poly- Poly- Iso- Mineral E, CH4 CHq 03H; 05H; 03H4 (13H9 Iene lena propymer23 octane Seal Total Dimer Trimer lcne Oil Cracking Furnace Eiuent- 276 444 46 3,795 3,773 160 44 8,538 Deacetylizer Eliuent 272 444 3,844 3,773 160 44 3,837 Propylene Polymerization Zone Eluent-; 272 444 3, 844 3,773 42 44 118 3, B37 Polymer Absorber Oil 10,770 10,770 Polymer Absorber Bottoms 6 6 9 10 118 10,770 10, 913 Polymer Absorber Overhead Product 272 444 3, 839 3, 767 33 8, 389 Ethylene Absorber 011---- 24, 520 Ethylene Absorber Bottoms- 3,724 3,754 32 24,520 32,064 Ethylene Absorber Over- Bhead ProdPu:t ri Ei 272 444 115 13 0.4 844 y-passedo yme a on Dilnent 161, 480 161,480 Ethylene Polymerization v Zone Feed 3,724 3, 754 32 34 186, 000 193, 544 Ethylene Polymerization Zone Eiiiuent-- 185 3,754 34 1 2 3,568 186,000 193,544 Flash Chamber Overhead Product 185 3,754 34 1 182,100 186,176 Flash Chamber Bottoms-- f 3, 568 3, 900 Polymer Column Bottoms- 1 Recycle Column Femm* 182, 099 182, 090 Recycle Column Liquid Overhead Product--- 1 1 Purge as 185 3, 754 34 3, 973 Make-up Polymerization lDiluent 3,901 3,901

.ITim-nn in d uan es poun s. Crarlng furnace feed: Ethane 8,538 pounds Ethylene conversion in polymerization zone.: 95 percent. All ethylene polymerization o-gas is purged. More isooetane is required in polymerization zone containing 95 percent ethane and as the remainder methane and some propane is cracked at a temperature (turnace effluent) of 150G F. and at a pressure (furnace effluent) of about 5 p. s. The gases after passing through a knock-out drum, not shown, are compressed to a pressure of about 50 p. s. i. g. and cooled to about 400 F. and pas-sed over a nickel suliidc, acetylene removal catalyst, relying on the hydrogen in the feed to convert the acetylene to ethylene. The acetylene-free gases are then passed over a phosphoric acid, propylene polymerization catalyst thus converting a substantial proportion of the propylene. The propylene polymerization catalyst in this instance is a phosphoric acid catalyst, and conditions are selected to polymerize a substantial part but not all of the propylene. The gases thus obtained are contacted with mineral seal oil to absorb from them the propylene polymer thus formed. The resulting gases are compressed to about 300 p. s. i. g., cooled to about 0 F. and then contacted with isooctane to absorb substantially all of the ethylene therefrom into the isooctane. The solution of ethylene in isooctane thus obtained is then pumped, together with additional isooctane being recycled from an earlier conversion step, into a zone containing a chromium oxide ethylene polymerization catalyst, as described herein, and in Serial No. 333,576, tiled January 27, 1953, above mentioned, and therein subjected to -solid polyethyleneforming conditions at a temperature of about 300 F. and a pressure of about 400 p. s. i. g. The polymer thus formed contains some propylene which is polymerized with the ethylene. Efliuent from the polymerization zone is then heated to about 380 F. and ashed at a pressure of 'about 20 Tp. s. i. g. to recover as overhead a substantial than is required in ethylene absorber.. The additional isooctane is introduced between the absorber 'and reactor.

i. g. to produce the feed shown.

It is noted, especially, that the absorber liquid-diluent of the present invention is inert and, therefore, it can be reused indefinitely; further that because the same liquid is employed in both the absorber and in the polymerization steps it performs a multiple of services lending considerable economy to the operation.

The products of this invention are either tacky, semisolid, or solid polymers of ethylene.

While the operations of the specic embodiments of the invention are preferred to be conducted with conditions to maintain substantially liquid phase in the ethylene polymerization zone, partial vapor phase operation is possible even to the extent that substantially all of the ethylene is in the vapor phase while at least a portion of the solvent is in the liquid phase.

The pressure must be high enough to maintain the diluent in the liquid phase and to assure that olens not liquefied under these conditions are dissolved in the liquid phase' in sufficient amount.

The reaction may be carried out in a lixed-bed or a moving-bed catalyst chamber. The reaction may also be effected in a catalyst slurry with the reaction product taken ol for purification and the catalyst to be regenerated taken off as a slurry, washed to remove occluded hydrocarbons, and passed on to regeneration. The regeneration is accomplished by oxidizing the residual coke and heav'y polymer deposit with a controlled c'oncentration-of oxygen in an inert gas by conventional procedures. Suspended catalyst techniques can also be employed.

It will be understood that the embodiments herein described are inclusive of the 'requisite pumps, compressors, heaters, coolers, valves vand other equipment which ordinarily will be employed in the routine execution of the invention. Also, details and steps of operation, for example, temperature regulation or the establishment of conditions optimum for each step of the claimed invention, are included within the scope of the appended claims.

ln the claims, it will be understood that the word solid applies also to include semi-solid and/or tacky products which not being liquids at ordinary temperatures are defined as solids. It is products such as these to which the terminology high molecular weight polymer is intended to be applied.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, drawings, and the appended claims to the invention, the essence of which is that there have been provided, as described, a combination of steps of absorption of ethylene from gases containing the same and subjecting the combined mixture of absorption medium and ethylene contained therein to polymerization conditions, in the presence of a catalyst, adapted to form a polyethylene, as described; a combination of steps in which, when propylene and other gases in undesirable amounts are contained in the absorption medium after contact with said gases, the mixture of absorption medium and gases in it is first subjected to a polymerization or other conversion operation, or operations, to remove therefrom any undesirable amounts of gases present therein, for example, to remove acetylene and/or undesirable amounts of propylene; and a combination for feeding step-wise tov a plurality of points within a system, through which is passing a sol-v,

vent containing a vaporous material, the concentration of which material in said solvent is reduced by i'tlswclonversion in said system, which comprises absorbing *said material in said solvent, dividing the solution thus obtained into at least two portions, feeding at leastrone portion to a point in said system, converting said material in said solvent, passing said solvent to another point in said system, passing at least one portion of said solution to a stripper in which it is made to yield up a substantial portion of said vaporous material, passing said vaporous material obtained from said stripper to said another point in said system together with the solvent being passed to said point and at said point converting said vaporous material, obtained from said stripper, dissolved in said solvent.

I claim:

1. A process for producing a solid polymer of ethylene and a liquid polymer of an olefin having a molecular weight higher than ethylene which comprises contacting an olefin feed material comprising ethylene and an olefin of higher molecular weight and lighter materials with a liquid hydrocarbon absorbent which is inert and non-deleterious under hereinafter described polymerization conditions whereby the ethylene and olefins of higher molecular weight are absorbed and freed from the lighter materials and passing the olefin feed mixture through a polymerization zone in which the predominant reaction is polymerization of ethylene to solid polymer and a polymerization zone in which the predominant reaction is polymerization of said olefin having a molecular weight higher than ethylene olefin feed mixture being introduced sequentially from one of said zones to the other of said zones.

2. A combination process for the production of a polymer of propylene and a normally solid polymer of ethylene which process comprises the following steps in combination: passing a gas stream comprising ethylene and propylene together with lighter materials including hydrogen into a first polymerization zone containing a polymerization catalyst and maintained under conditions suitable for the selective polymerization of propylene, therein effecting polymerization of propylene to normally liquid polymers without substantial polymerization of ethylene; passing a hydrocarbon effluent from said first polymerization zone to a first absorption zone, contacting the hydrocarbon efiluent with a normally liquid hydrocarbon oil under absorption conditions such that normally liquid polymer of propylene is selectively absorbed in said oil; removing an enriched oil from said first absorption zone and recovering propylene polymer therefrom; passing a gaseous effluent from said first absorption zone to a second absorption zone and therein contacting said eiuent with a hydrocarbon solvent which is liquid under the absorption conditions and liquid and inert under polymerization conditions subsequently described, thereby absorbing ethylene in said solvent; removing materials lighter thanethylene from the system; withdrawing an ethylene-enriched solvent from said second absorption zone and passing the enriched solvent to a second polymerization zone wherein said enriched solvent is contacted with a composite chromium oxide catalyst at a temperature in the range 225 to 350 F. and a pressure sufficient to maintain said solvent substantially in the liquid phase; withdrawing an efiiuent from said second polymerization zone; and recovering a normally solid polymer fromsaid eiuent.

3. A process which comprises introducing a normally gaseous mixture comprising ethylene and propylene together with lighter gases into an absorption zone and therein contacting said mixture with a liquid hydrocarbon which is inert and liquid under polymerization conditions subsequently described herein; absorbing ethylene and propylene in said hydrocarbon; withdrawing material lighter than ethylene from the system; passing enriched hydrocarbon solvent from said absorption zone to a first polymerization zone containing a catalyst which catalyzes the polymerization of propylene but does not substantiallycatalyze the polymerization of ethylene, said polymerization zone being maintained under temperature and pressure conditions suitable for the polymerization of propylene to lliquid polymer; effecting the polymerization of propylene without substantial polymerization of ethylene; passing a resulting etiiuent from said first polymerization zone to a second polymerization zone maintained at a temperature in the range 225 to 350 F. and a pressure sufficient to maintain said effluent substantially in the liquid phase; contacting said effluent with a catalyst comprising chromium oxide in said second polymerization zone; fractionating a hydrocarbon mixture effluent from said second polymerization zone and recovering therefrom a normally solid polymer, at least one normally liquidpolymer of propylene, and said solvent.

4. A process which comprises supplying a normally gaseous stream comprising ethylene and propylene together with other gaseous hydrocarbons and hydrogen to a first catalytic polymerization zone; effecting polymerization of part of said propylene to liquid polymer in said first polymerization zone without substantial polymerization of said ethylene; passing a resulting hydrocarbon mixture to a first absorption zone and therein contacting said mixture With a hydrocarbon absorption oil, thereby absorbing propylene polymer in said oil; withdrawing enriched oil from 'said first absorption zone and recovering propylene polymer therefrom; passing a gaseous mixture containing ethylene and unpolymerized propylene from said first absorption zone to a second absorption zone and therein absorbing ethylene and unpolymerized propylene in a liquid hydrocarbon solvent which is liquid and inert under polymerization conditions subsequently described; passing enriched solvent from said second absorption zone to a second polymerization zone maintained at a temperature in the range of 225 to 350 F. and a pressure suficient to maintain saidV solvent substantially in the liquid phase; in said second polymerization zone, contacting said enriched solvent with a catalyst comprising chromium oxide, whereby a normally solid copolymer of ethylene and propylene is formed; passing a resulting mixture from said second polymerization zone to a recovery zone and therein recovering said copolymer.

A process for the production of a solid polymer which process comprises cracking a hydrocarbon stream to produce a mixture of gases containing hydrogen, methane, acetylene, ethylene, ethane, propane, and propylene; subjecting said mixture to conditions suitable for the removal of acetylene therefrom; subjecting a resulting stream essentially free from acetylene to catalytic polymerization to produce and remove therefrom a liquid propylene polymer; subjecting the remaining gaseous stream to absorption conditions in an absorption zone and therein absorbing ethylene in a hydrocarbon solvent which is liquid and nonpolymerizable; subjecting a resulting mixture of solvent and ethylene to temperature and pressure conditions suitable for the formation of a solid polymer of ethylene, and recovering a solid polymer of ethylene.

6. A process for the production of ethylene polymer and propylene polymer from a cracked gas comprising ethylene and propylene, which process comprises polymerizing at least part of said propylene under conditions suitable for the selective polymerization of said propylene to liquid polymer without substantial polymerization of ethylene, absorbing ethylene in a solvent, subsequently described, to form an ethylene-enriched solvent, passing said ethylene-enriched solvent to a polymerization zone wherein ethylene is polymerized in the presence of a hydrocarbon solvent which is liquid and inert under the polymerization conditions to produce a solid polymer of` ethylene and recovering said solid polymer and a liquid propylene polymer.

polymerization catalyst.A t

8. A process according to lclaiml 'wherein' a cracked gas containing ethylene and propylene` is absorbed into said adsorbent,'the enriched adsorbent is subjected "to propylene polymerization conditions, and the thus treated.

adsorbent is subjected to ethylene polymerization conditions to produce said polyethylene.

9. A process according to claim 1 wherein the effluent from the ethylene polymerization zone is separated into solvent, which is returned to the absorption step for reuse, a C12 polymer, propylene dimer, unreacted gases and a solid polyethylene.

l0. A process for the production of a solid polymer which comprises cracking a hydrocarbon stream to produce a stream of gases containing hydrogen, methane, acetylene, ethylene, ethane, propane, and propylene, subjecting said gaseous stream to conditions suitable for the removal of acetylene therefrom, then subjecting said stream to catalytic polymerization to produce and remove therefrom, as a product of the process, a liquid propylene polymer, then subjecting the Iremainder of said stream to ethylene-absorbing conditions to absorb ethylene into a nonreactive solvent which remains nonrcactive under conditions suitabie for the polymerization of ethylene to a solid polyethylene, then subjecting said thus-absorbed ethylene to solid polyethylene-forming conditions in the presence of a chromium oxide polymerization catalyst containing hexavalent chromium, and then recovering solid polyethylene from said solvent.

l1. A process for the production of solid polymer 'according to claim wherein the ethylene and solvent mix- 30 7. A process according to claim 6 wherein the propylene is polymerized in the presence of a phosphoric acid ture is divided into at least two streams, a first stream is passed to at least one of several polymerization zones, maintained under polymerization conditions suitable for the production of said polyethylene, another stream which is passedjto a stripper and therein caused to yield up a substantial portion of its dissolved ethylene, and wherein thus recovered ethylene is passed to at least one other of said zones maintained under said last-mentioned conditions.

l2. A process according to claim l1 wherein .the solvent is passed from the lirst mentioned polymerization zone to the second mentioned polymerization zone and the ethylene passed to said second mentioned polymerization zone is admixed with said solvent passed to said second mentioned polymerization zone before said solvent has substantially entered said zone.

13. A process according'to claim '11 wherein the solvent containing ethylene obtained from the ethylene absorbing step is pumped to a pressure substantially above that of said polymerization zones, is divided into said at least two streams and wherein the stream passedto said stripper is heated to yield up a portion of its ethylene thus obtaining ethylene at a high pressure sutr'cient to feed the same to said zones'.

14. In a method of feeding to a plurality of polymerization conversion zones vin a system'a vaporous material comprising ethylene under a pressure sucient to accomplish said feeding at a plurality 'ofv points in .the system, in which a solvent isernployed to absorb said material and convey,k it vthrough each of said zones, the steps comprising, Vfeeding said material vto `an` absorber zone, therein contacting "saidI material under absorbing conditionsv with "said 'solvent 'to Iform a solution of .said material .infsaidsolvetzat e :pressure jsuicient' to accomplish said feedin'gatia'plurlity of points in 'the system, removing Lsaid solution from said absorber zone, dividing said solution into atleast two jportions, `feeding atleast one of said portions ot"`said polmerization solutionto at least one of said conversion'zones, wherein the vaporous material is converted and wherein the solvent remains substantially unatected,"passing said solvent'to another polymerization conversion zone, passing atleast another portion Yof said solution, obtained from said absorber zone, to a stripper zone wherein said solution is made to yield up a substantial quantity of said vaporous material, and passing said vaporous material to said solvent being passed to said another polymerization conversion zone, in said another polymerization conversion zone converting said vaporous material and leaving said solvent substantially unaffected, and finally, recovering solvent and converted material from said last mentioned polymerization ZODC.

15. A method according to claim 14- wherein solvent from the stripper zone is returned to the absorber zone for absorbing additional quantities of said vaporous material and wherein a solvent recovered from said last mentioned conversion zone is also retumed to the system for reuse.

References Cited in the le of this patent UNITED STATES PATENTS 2,691,647 meldt-; oct. 12, 1954 UNITED- STATES PATENT OFFICE CERTIFICATE 01E-CORRECTION Patent No. 2,827,444 Y E March 1E, 195s Martin R. cines Column .3, lline 45, for "isoocatane" read sooctane lines 52 and 60, for "isoctzane'l read isooctane line '70, for "catalyst 230" read catalysll 23 vcolumn 4, line 9, for {'isoctane" read isooctane line 58, for "miner" read mineral column 9, lne 62, after "ethylene" insert a comma; column ll, line 40, forl the claim reference numeral "l", read 6 --3 column l2, line 38, after "said" strike out ''polymezc'izat ion'f and inser'l the -same after "saidWand before "conversion" in line 39, same column. 4 d

signed and sealed this 29th day of July 1958. (SEAL) Atest: KARL H. AXLINE ROBERT C. WATSON Attesting Officer Conmissioner of Patents 

2. A COMBINATION PROCESS FOR THE PRODUCTION OF A POLYMER OF PROPYLENE AND A NORMALLY SOLID POLYMER OF ETHYLENE WHICH PROCESS COMPRISES THE FOLLOWING STEPS IN COMBINATION: PASSING A GAS STREAM COMPRISING ETHYLENE AND PROPYLENE TOGETHER WITH LIGHTER MATERIALS INCLUDING HYDROGEN INTO A FIRST POLYMERIZATION ZONE CONTAINING A POLYMERIZATION CATALYST AND MAINTAINED UNDER CONDITIONS SUITABLE FOR THE SELECTIVE POLYMERIZATION OF PROPYLENE, THEREIN EFFECTING POLYMERIZATION OF PROPYLENE TO NORMALLY LIQUID POLYMERS WITHOUT SUBSTANTIAL POLYMERIZATION OF ETHYLENE; PASSING A HYDROCARBON EFFLUENT FROM SAID FIRST POLYMERIZATION ZONE TO A FIRST ABSORPTION ZONE, CONTACTING THE HYDROCARBON EFFLUENT WITH A NORMALLY LIQUID HYDROCARBON OIL UNDER ABSORPTION CONDITIONS SUCH THAT NORMALLY LIQUID POLYMER OF PROPYLENE IS SELECTIVELY ABSORBED IN SAID OIL; REMOVING AN ENRICHED OIL FROM SAID FIRST ABSORPTION ZONE AND RECOVERING PROPYLENE POLYMER THEREFROM; PASSING A GASEOUS EFFLUENT FROM SAID FIRST ABSORPTION ZONE TO A SECOND ABSORPTION ZONE AND THEREIN CONTACTING SAID EFFLUENT WITH A HYDROCARBON SOLVENT WHICH IS LIQUID UNDER THE ABSORPTION CONDITION AND LIQUID AND INERT UNDER POLYMERIZATION CONDITIONS SUBSEQUENTLY DESCRIBED, THEREBY ABSORBING ETHYLENE IN SAID SOLVENT; REMOVING MATERIALS LIGHTER THAN ETHYLENE FROM THE SYSTEM; WITHDRAWING AN ETHYLENE-ENRICHED SOLVENT FROM SAID SECOND ABSORPTION ZONE AND PASSING THE ENRICHED SOLVENT TO A SECOND POLYMERIZATION ZONE WHEREIN SAID ENRICHED SOLVENT IS CONTACTED WITH A COMPOSITE CHROMIUM OXIDE CATALYST AT A TEMPERATURE IN THE RANGE 225 TO 350*F. AND A PRESSURE SUFFICIENT TO MAINTAIN SAID SOLVENT SUBSTANTIALLY IN THE LIQUID PHASE; WITHDRAWING AN EFFLUENT FROM SAID SECOND POLYMERIZATION ZONE; AND RECOVERING A NORMALLY SOLID POLYMER FROM SAID EFFLUENT. 